This invention relates to a substitution of adjustable valve packings around reciprocating stems for control valves and the like that see considerable amounts of motion; and where such conventional packings could wear, and as a result, open leakage paths for the fluid between the valve interior and the outer-atmosphere at the given valve location. This is especially hazardous where the valve is handling poisonous or radioactive substances.
Bellows seals, either in the hydroformed configuration or fabricated from metal rings welded together, are not new and well understood by persons skilled in the art, see example U.S. Pat. No. 2,956,771.
The problem with such conventional, state-of-the-art stem seals is that at least one terminating end of such bellows has to be welded to the device that has to be sealed. This makes the replacement very difficult and costly. The other drawback of present state-of-the-art designs is found in a way that valve stems are kept from rotating. Any attempt of forced rotation from the actuator side of a valve stem to a permanently fixed interconnection between stem and bellows (usually by welding) will twist such a bellow and cause mechanical failure. Conventional constructions, therefore, use profiled stems, such as a hexagonal cross-section, sliding in a similar hexagonal bearing port, or by employing a radial pin within part of the stem, which slides in a grooved slot as part of a companion static valve part in order to avoid rotation. All these methods are very expensive to produce and also add unnecessary bulk to such an assembly. Finally, existing bellows designs cannot employ conventional valve plugs that are normally used with valves which employ conventional stem packing. Again, this is due to requirements for welded connections. This leads to a major maintenance problem by users and adds increased manufacturing costs to the assembly.
My invention overcomes all these drawbacks by providing a bellows assembly that:
a. requires no welded connections,
b. allows the use of conventional, pinned valve plugs that can easily be field replaced; and
c. provides a way to allow free rotation of the valve stem without inputting torsion onto the bellows and yet be able to lift both bellows and valve plug up and down.
These and other advantages and novel results will become apparent in view of the annexed drawings and the following descriptions.